This invention relates to insulation products which include an infrared radiation blocking agent, and more particularly to insulation products which include chiral materials designed to block the transmission of infrared radiation.
Insulation products are designed to prevent or at least reduce heat flow between two surfaces. It is well known in the art that use is made of glass or other mineral, organic, or natural (i.e., cellulose, cotton, wool, etc.) fibrous blankets to insulate buildings or smaller structures.
Heat is transferred between two surfaces having a temperature differential therebetween by three major mechanisms--conduction, convection, and radiation. Thus, in the typical situation, for example, there is air in a gap between two surfaces in a building wall or roof. The insertion of insulation such as glass wool fibers into the gap greatly reduces convection as a heat transport mechanism as the insulation slows or stops the circulation of air. Heat transfer by conduction through the glass fibers themselves, which constitute less than 1% of the total insulated cavity volume, is also minimal. However, most glass compositions used in glass wool insulation products are transparent to portions of the infrared spectrum. Thus, heat transfer by radiation remains a significant mechanism, even where the gap has been insulated, and may account for from about 10 to 40% of the heat transferred between surfaces.
Some attempts have been made to reduce this radiant heat transfer by including certain additives into the glass compositions which would block infrared radiation. Boron has been used for this purpose. However, many of the effective additives are environmentally undesirable as additives to glass. Further, such additives are capable of blocking radiation only in certain small wavelength bands, not across the entire infrared spectrum.
Accordingly, the need still exists in the art for an insulation product which can effectively block the transmission of infrared radiation.